JP4645508B2 - Backlight device and lighting device - Google Patents

Description

  The present invention relates to a backlight device and an illuminating device, and more particularly to a technique for suppressing moving stripes generated in a mercury discharge lamp.

The backlight device generally includes a mercury discharge lamp. Mercury discharge lamps may cause a phenomenon called moving stripes (striations) depending on lighting conditions. If moving stripes occur, the brightness of the lamp flickers. Techniques for suppressing such brightness flickering of the lamp are disclosed in, for example, Patent Document 1 and Patent Document 2.
FIG. 14 is a diagram showing a configuration of the lamp lighting device disclosed in Patent Document 1. As shown in FIG.

  The lamp 11 is lit by receiving power from the AC power supply 12 via the ballast 13. The lamp current asymmetry means 14 makes the lamp current of the lamp 11 DC biased to make the positive and negative current values of the lamp current asymmetric. According to Patent Document 1, such a configuration causes a moving stripe on the lamp 11, but the stripe moves at a high speed. It is described that flickering can be substantially prevented, or even if brightness flickering occurs, the flickering disappears in a short time.

FIG. 15 is a diagram showing a configuration of the lamp lighting device disclosed in Patent Document 2. As shown in FIG.
The discharge lamp 45 is lit by receiving power supply from the lighting circuit 41. When the lighting circuit 41 is dimmed, if the ambient temperature detected by the temperature detection circuit 44 falls below a predetermined temperature, the switching circuit 42 forces the lighting circuit 41 to perform rated lighting. Patent Document 2 describes that such a configuration can prevent extinction at low temperatures. Although not explicitly disclosed in Patent Document 2, if the rated lighting is forcibly turned on, the ambient temperature of the discharge lamp 45 increases, so it is presumed that there is also an effect of suppressing moving stripes.
Japanese Patent Publication No. 64-3318 Japanese Patent Publication No. 7-46636

  However, in the technique disclosed in Patent Document 1, since a DC bias is applied over a long period of time, there is a possibility that a so-called cataphoresis phenomenon occurs in which the distribution of mercury is biased and a luminance difference occurs between both ends of the lamp. In particular, in the case of a backlight device for a liquid crystal display, when a cataphoresis phenomenon occurs in the lamp, the uniformity of the display is deteriorated, and the image quality is deteriorated.

Further, in the technique disclosed in Patent Document 2, since the rated lighting is forcibly performed when the ambient temperature is low, control such as adjusting the luminance of the backlight according to the brightness of the room cannot be performed at all. There is a problem.
These problems occur not only in the backlight device but also in the lighting device.

  Therefore, the present invention provides a backlight device and an illumination device that can suppress the observation of moving fringes without depending on any of the measures of applying a DC bias and forcibly lighting at rated power. The purpose is to provide.

  The backlight device according to the present invention comprises a mercury discharge lamp in which internal electrodes are disposed at both ends of a glass tube, and an outer periphery of a substantially central portion in the tube axis direction of the glass tube of the mercury discharge lamp. A high frequency voltage is applied between the electric resistance member arranged so as to contact the surface and an internal electrode disposed in the mercury discharge lamp, and a high frequency voltage is applied between the internal electrode and the electric resistance member. High-frequency voltage applying means.

  An illumination device according to the present invention comprises a mercury discharge lamp in which internal electrodes are disposed at both ends of a glass tube, and an outer peripheral surface of a substantially central portion in the tube axis direction of the glass tube of the mercury discharge lamp. A high frequency voltage that applies a high frequency voltage between the electrical resistance member disposed in contact with the internal electrode and an internal electrode disposed in the mercury discharge lamp, and applies a high frequency voltage between the internal electrode and the electrical resistance member Voltage applying means.

The inventors of the present application conducted an experiment to observe moving fringes while increasing the tube wall temperature (cold spot temperature) of the mercury discharge lamp. As a result, the existence of a threshold temperature at which no moving fringes are observed can be confirmed. did it. It was also found that the threshold temperature is determined by the shape of the mercury discharge lamp, etc., and does not depend on the ambient temperature.
According to the said structure, an internal electrode, an electrical resistance member, and a glass tube comprise a capacitor equivalently. Therefore, when a high frequency voltage is applied between the internal electrode and the electric resistance member, a current flows through the electric resistance member. As a result, Joule heat is generated in the electric resistance member, and the temperature at the substantially central portion in the tube axis direction of the glass tube that is near the coldest point of the mercury discharge lamp rises. In this way, by using an electric resistance member to raise the temperature near the coldest point of the mercury discharge lamp, regardless of any measures of applying a DC bias and forcibly lighting the rated voltage, Observation of moving fringes can be suppressed.

The electric resistance member is fixed to a curved portion having a curved surface along an outer peripheral surface of a glass tube of the mercury discharge lamp, and a backlight device casing, and the mercury discharge lamp is mounted on the curved surface of the curved portion. It is good also as providing the support site | part which supports the said curved site | part in the state which fitted the glass tube.
In general, a tubular mercury discharge lamp is used for the backlight device. Therefore, in the backlight device, the mercury discharge lamp tends to be easily damaged due to vibration during transportation. According to the said structure, an electrical resistance member also has an effect of controlling the vibration of the approximate center part of the tube axis direction of the glass tube of a mercury discharge lamp further. Therefore, it is possible to prevent the mercury discharge lamp from being damaged by vibration of the substantially central portion of the glass tube in the tube axis direction during transportation of the backlight device. Note that, in the case of using a thin tubular mercury discharge lamp not only in the backlight device but also in the lighting device, it is effective from the viewpoint of preventing the mercury discharge lamp from being damaged when the above configuration is used.

Moreover, the electrical resistance value of the part adjacent to the curved part of the support part may be larger than the electrical resistance value of the part not adjacent to the curved part.
Further, the electric resistance value of the curved portion may be larger than the electric resistance value of the support portion.
According to the said structure, the site | part near a mercury discharge lamp can be heated. Therefore, the amount of heat can be efficiently transmitted to the mercury discharge lamp.

  The high-frequency voltage applying means includes a high-frequency power supply unit that outputs a high-frequency voltage of a predetermined frequency, and a first wire that is inserted in a wiring for applying the high-frequency voltage output by the high-frequency power supply unit between the internal electrodes. And a second resonance frequency inserted in a wiring for applying a high-frequency voltage output from the high-frequency power supply unit between the internal electrode and the electric resistance member. It is good also as a 2nd resonance circuit which has.

According to the above configuration, the circuit for applying the high frequency voltage between the internal electrodes and the circuit for applying the high frequency voltage between the internal electrode and the electric resistance member can share the high frequency power supply unit. Therefore, the configuration can be simplified as compared with the case where a high frequency power supply unit is separately provided in each circuit.
Further, the backlight device further adjusts the frequency of the high-frequency voltage output from the high-frequency power supply unit to a dimming ratio in a frequency region sandwiched between the first resonance frequency and the second resonance frequency. It is good also as providing the frequency setting means to set to the frequency according to.

  According to the above configuration, if the current flowing between the internal electrodes is decreased by changing the frequency of the high-frequency voltage, the current flowing between the internal electrode and the electric resistance member increases. Therefore, even if the current flowing between the internal electrodes is decreased and dimming is performed, the Joule heat generated in the electric resistance member is increased, so that the cold spot temperature of the mercury discharge lamp can be prevented from being lowered. it can.

  Further, the backlight device further sets the frequency of the high-frequency voltage applied between the internal electrode and the electric resistance member until a predetermined period elapses after the application of the high-frequency voltage between the internal electrodes is started. The first frequency is set, and the frequency of the high-frequency voltage applied between the internal electrode and the electric resistance member is set to a second frequency lower than the first frequency when the predetermined period elapses. It is good also as providing a frequency setting means.

  In general, the coldest spot temperature of a mercury discharge lamp is the lowest immediately after the start of lighting, and rises with time. That is, the moving stripes are easily observed immediately after the lighting starts. According to the above configuration, the current flowing between the internal electrode and the electric resistance member can be made larger after the predetermined period has elapsed from immediately after the start of lighting until the predetermined period elapses. Therefore, the cold spot temperature of the mercury discharge lamp can be increased faster than in the case where the current flowing between the internal electrode and the electric resistance member is constant. As a result, it is possible to suppress the situation in which moving stripes are observed.

The mercury discharge lamp may be a hot cathode fluorescent lamp.
By using a hot cathode type fluorescent lamp, effects such as cost reduction can be achieved as compared to using a cold cathode type fluorescent lamp. The hot cathode fluorescent lamp needs to accommodate an electrode made of a filament coil, and therefore has a larger lamp tube diameter than the cold cathode fluorescent lamp. For this reason, the width of the bright and dark portions of the moving fringes is wide, and the moving fringes tend to appear remarkably. When trying to suppress the movement fringes using the technique disclosed in Patent Document 1, the hot cathode fluorescent lamp must have a larger DC bias than the cold cathode fluorescent lamp. As a result, there is a problem that it is easy to induce a cataphoresis phenomenon. According to the present invention, since generation of moving fringes is suppressed without applying a DC bias, a high effect can be obtained particularly when a hot cathode fluorescent lamp is used.

The best mode for carrying out the present invention will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a diagram illustrating a schematic configuration of a backlight device according to Embodiment 1.
The backlight device includes a mercury discharge lamp 1, a lighting circuit 2, an electric resistance member 3, a housing 4, and a reflection plate 5.

The mercury discharge lamp 1 is formed by disposing internal electrodes at both ends of a glass tube. The internal electrode is electrically connected to the lighting circuit 2 through the wiring 6. The mercury discharge lamp 1 is specifically a hot cathode fluorescent lamp, a cold cathode fluorescent lamp, or the like.
The lighting circuit 2 applies a high frequency voltage between the internal electrodes disposed in the mercury discharge lamp 1 and applies a high frequency voltage between the internal electrode and the electric resistance member 3. Thus, a lamp current is supplied between the internal electrodes by applying the high-frequency voltage between the internal electrodes. Further, a heating current is supplied between the internal electrode and the electric resistance member 3 by applying a high-frequency voltage between the internal electrode and the electric resistance member 3. Here, the high frequency means a frequency generally used in the inverter lighting system.

The electric resistance member 3 is made of an electric resistance material, and is arranged so as to be in contact with the outer peripheral surface of the substantially central portion in the tube axis direction of the glass tube of the mercury discharge lamp 1. In the first embodiment, the electric resistance member 3 is fixed to the housing 4 and grounded via the housing 4 and the wiring 8.
The housing 4 houses the mercury discharge lamp 1 and the reflection plate 5. In the first embodiment, the housing 4 is made of a conductive member and is grounded via the wiring 8. The reflection plate 5 reflects the light emitted from the mercury discharge lamp 1 toward the reflection plate 5 toward the front surface.

If a diffusion plate or a liquid crystal panel is arranged in front of the backlight device, a liquid crystal display can be configured.
FIG. 2 is a view showing the appearance of the electric resistance member 3.
2A is a perspective view, and FIG. 2B is a front view.
The electrical resistance member 3 is made of an electrical resistance material, and includes a curved portion 31 and a support portion (consisting of an adjacent portion 32 and a non-adjacent portion 33). The curved portion 31 has a curved surface along the outer peripheral surface of the glass tube of the mercury discharge lamp 1. The support part is fixed to the housing 4 and supports the curved part 31 in a state where the glass tube of the mercury discharge lamp 1 is fitted on the curved surface of the curved part 31. The electrical resistance material is a material having electrical resistivity and conductivity. For example, metal or carbon can be considered.

  In the example shown in FIG. 2, the diameter of the adjacent portion 32 adjacent to the curved portion 31 among the support portions is made smaller than the diameter of the non-adjacent portion 33 not adjacent to the curved portion. Therefore, if the electrical resistance material is the same in the adjacent portion 32 and the non-adjacent portion 33, the electrical resistance value of the adjacent portion 32 is larger than the electrical resistance value of the non-adjacent portion 33. Therefore, it is possible to selectively generate heat in the vicinity of the mercury discharge lamp.

In addition, the electrical resistance member 3 has a function of fixing the mercury discharge lamp 1 and the housing 4 by providing a support portion. As a result, not only the heating current is allowed to flow, but also the vibration at the substantially central portion of the tube axis of the glass tube of the mercury discharge lamp 1 can be regulated.
FIG. 3 is a view showing a modification of the electric resistance member 3.
FIG. 3A shows an example in which the adjacent portion of the support portion adjacent to the curved portion is formed of the material R1 having a high electrical resistivity. FIG. 3B shows an example in which the curved portion is made of a material R1 having a high electrical resistivity. In any case, a desired electrical resistance value can be secured by appropriately selecting the material and shape.

In these examples, the electric capacity resulting from the electric resistance member 3 is defined by the surface area of the curved surface of the curved portion. However, the present invention is not limited thereto, and the electric capacity may be defined by the surface area of the conductive film by forming a conductive film on the glass tube and bringing the curved portion into contact with the conductive film. By doing so, a larger current can be passed through the electric resistance member 3.
If attention is paid only to the function of supplying a heating current, the support part is not an essential element, and wiring may be provided instead of the support part.

FIG. 4 is a circuit diagram showing details of the lighting circuit 2 according to the first embodiment.
Switching elements Q1 and Q2 are connected in series between the positive electrode and the negative electrode of the DC power supply VDC. A first resonance circuit, a second resonance circuit, and a filament current supply circuit are connected between the source and drain terminals of the switching element Q2.
The first resonance circuit includes an inductor L1 and a capacitor C1. A primary coil of the capacitor C3 and the transformer T1 is connected in series between the terminals of the capacitor C1. The capacitor C3 is a capacitor that prevents direct current from being input to the primary coil of the transformer T1. The internal electrode of the mercury discharge lamp 1 is connected to the secondary coil of the transformer T1. With this configuration, a high-frequency voltage appears between the terminals of the capacitor C1 according to the lighting frequency, and the high-frequency voltage is boosted by the transformer T1 and applied between the internal terminals of the mercury discharge lamp 1.

  The second resonance circuit includes an inductor L1, a capacitor C2, a capacitor C4, and an electric resistance R1. As described above, in the first embodiment, the first resonance circuit and the second resonance circuit share the inductor L1. By sharing the inductor L1, the lighting circuit 2 can be reduced in size and cost. The capacitor C4 is a capacitor having the inside of the mercury discharge lamp 1 and the electric resistance member 3 as electrodes, and a glass wall sandwiched between them as a dielectric (see FIG. 4B). The electric resistance R1 is an electric resistance that the electric resistance member 3 has. With this configuration, a high-frequency voltage corresponding to the lighting frequency is applied between the internal electrode of the mercury discharge lamp 1 and the electric resistance member 3. As a result, a heating current flows through the electric resistance member 3.

  The filament current supply circuit includes a primary coil of the transformer T2 and a capacitor C5. The capacitor C5 is a capacitor that prevents direct current from being input to the primary coil of the transformer T2. The internal electrode of the mercury discharge lamp 1 is connected to the secondary coil of the transformer T2. With this configuration, a filament current corresponding to the lighting frequency is supplied to the internal electrode of the mercury discharge lamp 1.

The drive circuit 21 is a circuit that alternately turns on and off the switching elements Q1 and Q2 at a cycle corresponding to the lighting frequency. The DC power supply VDC, the switching elements Q1 and Q2, and the drive circuit 21 constitute a high frequency power supply unit.
In order to drive the switching elements Q1 and Q2, the driving circuit 21 outputs a driving signal to the respective gate terminals of the switching elements Q1 and Q2, and receives a voltage signal at a connection point between the switching elements Q1 and Q2. A variable resistor Rosc is connected between the resistance terminal of the drive circuit 21 and the ground, and a capacitor Cosc is connected between the capacitor terminal of the drive circuit 21 and the ground. The drive circuit 21 repeats the operation of charging the capacitor Cosc and discharging it through the variable resistor Rosc when the charge voltage reaches a predetermined voltage. A drive signal for driving the switching elements Q1 and Q2 is generated in synchronization with the repetition cycle. For this reason, the lighting frequency becomes higher as the repetition period is shorter.

The lighting frequency setting circuit 22 changes the resistance value of the variable resistor Rosc based on a user instruction or a result of automatic photometry. If the resistance value of the variable resistor Rosc is changed, the lighting frequency is changed, so that the lamp current is changed, and as a result, the dimming ratio is changed.
Here, a specific design will be described.
A DC voltage of 400V is used as the power source VDC. If the power supply is as low as 15V or 24V in the TV set situation, a booster circuit such as a boost chopper is provided between the power supply and the series connection body of the switching elements Q1 and Q2 to obtain a high voltage of about 400V. And

  The amount of heat generated by the electrical resistance member 3 is determined according to the lamp status and the unit status, and thus cannot be generally described, but a case where 1 W of electric power is supplied will be described as an example. The power supply voltage is 400 V, the heating current flowing through the electric resistance member 3 is set to 20 mA, and the lighting frequency is set to 100 kHz. The mercury discharge lamp 1 is broken down, and it is assumed that the voltage drop inside the lamp from the internal electrode of the mercury discharge lamp 1 to the electric resistance member 3 is 200V. When the capacitance of the capacitor C2 is 10 nF, the impedance of the capacitor C2 is about 160Ω. Then, the voltage drop at the capacitor C2 is about several volts.

  On the other hand, when the capacitance of the capacitor C4 is set to about 220 pF, the voltage drop at the capacitor C4 is about 145V. If it does so, the voltage applied to the electrical resistance member 3 will be 400V-200V-145V-several V, and will be about 50V. If the magnitude of the current flowing through the electric resistance member 3 is 20 mA and the voltage is 50 V, the electric resistance member 3 can consume 1 W of power if the resistance value of the electric resistance member 3 is 2500Ω.

Thus, the amount of heat generated by the electrical resistance member 3 can be controlled by controlling the lighting frequency or the high-frequency component of the voltage waveform.
FIG. 5 shows a high-frequency voltage waveform output from the lighting circuit 2.
FIG. 5A shows a pulse superimposed voltage waveform in which a pulse having a high peak value is superimposed on a sinusoidal waveform and includes a high frequency component. When this voltage is applied between the internal electrodes of the mercury discharge lamp 1, a high voltage is applied to both ends of the mercury discharge lamp 1, so that a heating current easily flows through the electric resistance member 3. As the frequency component included in this voltage waveform is increased, the ratio of the heating current to the current supplied from the lighting circuit 2 can be increased.

FIG. 5B shows a high frequency voltage waveform. By increasing the lighting frequency as shown in the section A at the time of starting or dimming, it is possible to make the heating current flow easily through the electric resistance member 3. As the frequency in the section A is increased, the ratio of the heating current to the current supplied from the lighting circuit 2 can be increased.
Next, regarding the relationship between the lamp current and the coldest spot temperature, the operating range when the ambient temperature is used as a parameter will be described.

FIG. 6 is a diagram showing the relationship between the lamp current and the coldest spot temperature.
Solid lines (a), (b), and (c) show the relationship between the lamp current and the coldest spot temperature when the dimming ratios are 100 (%), 50 (%), and 10 (%), respectively. Dashed lines (b), (b), (c), and (d) indicate the coldest spot temperatures at ambient temperatures of 25 (° C), 10 (° C), 0 (° C), and -10 (° C). . For example, if the ambient temperature Ta is 25 (° C.) and the dimming ratio is 50 (%), the temperature indicated by the intersection of the solid line (b) and the broken line (A) indicates the coldest spot temperature Tc of the mercury discharge lamp. It will be. Even when the ambient temperature is constant, the coldest spot temperature rises because the entire lamp is warmed by increasing the lamp current.

  The inventors of the present application conducted an experiment to observe moving fringes while increasing the tube wall temperature (cold point temperature) of the mercury discharge lamp, and confirmed the existence of a threshold temperature Tcc at which no moving fringes were observed. I was able to. It was also found that the threshold temperature Tcc is determined by the shape of the mercury discharge lamp, the composition and pressure of the sealed gas, and not the ambient temperature. As described above, the threshold temperature varies depending on the shape of the mercury discharge lamp or the like, but can be specified for each lamp by performing an experiment described later.

  In FIG. 6, for example, when the ambient temperature is 0 (° C.), if the dimming ratio is 100 (%), the coldest spot temperature Tc is higher than the threshold temperature Tcc, and thus no moving stripes are observed. However, when the dimming ratio is lowered from 100 (%) to 10 (%), the coldest spot temperature Tc eventually matches the threshold temperature Tcc (the lamp current at this time is Ila (a) ). If the dimming ratio is lowered below this, moving fringes will be observed.

  For example, when the light control ratio is 50 (%), if the ambient temperature is 0 (° C.), the coldest spot temperature Tc is higher than the threshold temperature Tcc, and thus no moving stripes are observed. However, as the ambient temperature decreases from 0 (° C.) to −10 (° C.), the coldest spot temperature Tc eventually matches the threshold temperature Tcc (the lamp current at this time is Ila (b )). If the ambient temperature falls below this, moving fringes will be observed.

FIG. 7 is a diagram illustrating the relationship between the lamp current and the lighting frequency and the relationship between the heating current and the lighting frequency.
A curve 31 shows the relationship between the lamp current and the lighting frequency. This relationship is determined by the characteristics of the first resonance circuit including the inductor L1 and the capacitor C1. Here, the inductance of the inductor L1 and the capacitance of the capacitor C1 are selected so that the resonance frequency of the first resonance circuit is lower than the frequency f1. Therefore, if the lighting frequency is increased from f1 to f2, the lamp current is decreased from Il1 to Il2.

  A curve 32 shows the relationship between the heating current and the lighting frequency. This relationship is determined by the characteristics of the second resonance circuit including the inductor L1, the capacitor C2, the capacitor C4, and the electric resistance R1. Here, the inductance of the inductor L1, the capacitance of the capacitor C2, and the capacitance of the capacitor C4 are selected so that the resonance frequency of the second resonance circuit is higher than the frequency f2. Therefore, if the lighting frequency is increased from f1 to f2, the heating current increases from Ir1 to Ir2.

With the above relationship, when dimming lighting is performed by reducing the lamp current, the heating current can be increased accordingly. Therefore, even if dimming is performed, it is possible to suppress a situation where the coldest spot temperature of the mercury discharge lamp is lowered.
(Embodiment 2)
FIG. 8 is a circuit diagram showing details of the lighting circuit 2 according to the second embodiment.

In the second embodiment, the capacitor C2 is connected to a connection point between the capacitor C3 and the transformer T1. Since the other configuration is the same as that of the first embodiment, the description thereof is omitted.
According to this configuration, the second resonance circuit includes the inductor L1, the capacitor C3, the capacitor C2, the capacitor C4, and the electric resistance R1. However, the capacitor C3 is a capacitor that prevents direct current from being input to the primary coil of the transformer T1, and uses a capacitor having a relatively large capacitance, and therefore hardly contributes to the frequency characteristics of the second resonance circuit. Therefore, the same electrical characteristics as in the first embodiment can be obtained.
(Embodiment 3)
FIG. 9 is a circuit diagram showing details of the lighting circuit 2 according to the third embodiment.

In the third embodiment, the capacitor C2 is connected to the connection point of the switching elements Q1 and Q2 via the inductor L2. Since the other configuration is the same as that of the first embodiment, the description thereof is omitted.
According to this configuration, the second resonance circuit includes the inductor L2, the capacitor C2, the capacitor C4, and the electric resistance R1. That is, the first resonant circuit and the second resonant circuit do not share the inductor L1, and a separate inductor L2 is provided. Therefore, since the first resonance circuit and the second resonance circuit can be designed separately, the degree of design freedom is improved. In particular, since the resonance frequency of the second resonance circuit can be brought close to the lighting frequency, a larger heating current can be passed.
(Embodiment 4)
FIG. 10 is a circuit diagram showing details of the lighting circuit 2 according to the fourth embodiment.

In the fourth embodiment, the arrangement of the inductor L3 is different from that in the third embodiment. Since the other configuration is the same as that of the third embodiment, the description thereof is omitted.
Even in this case, as in the third embodiment, the degree of freedom in design is improved. In particular, since the resonance frequency of the second resonance circuit can be brought close to the lighting frequency, a larger heating current can be passed.
(Embodiment 5)
FIG. 11 is a diagram showing the change over time of the voltage applied to the mercury discharge lamp 1 (fluorescent lamp).

A case where the mercury discharge lamp 1 is a hot cathode fluorescent lamp will be described.
During the preheating period, a filament current is supplied to the filament coil of the mercury discharge lamp 1 to emit thermoelectrons. At this time, since the electric power is actually supplied to the fluorescent lamp at the same time, a voltage that does not cause the fluorescent lamp to start is applied.
During the start-up period, the lighting frequency is lowered to approach the resonance frequency of the first resonance circuit, and the current flowing through the first resonance circuit is increased. Since the fluorescent lamp is not lit, the voltage applied to the fluorescent lamp increases and eventually breaks down to turn on the fluorescent lamp.

Thus, the heating current in the preheating period and the starting period can be increased by setting the lighting frequency higher in the preheating period and the starting period, and setting the lighting frequency lower when the starting period elapses.
(Embodiment 6)
FIG. 12 is a diagram showing a schematic configuration of the liquid crystal display.

The sixth embodiment differs from the first embodiment in that a liquid crystal panel 7 is mounted on the front surface of the housing 4. Since the other points are the same as those in the first embodiment, description thereof is omitted. As described above, even when there are a plurality of mercury discharge lamps, a heating current can be allowed to flow for each mercury discharge lamp as in the previous embodiments.
(Experiment and results)
The inventors conducted experiments to examine the coldest spot temperature when moving fringes are substantially not observed at various ambient temperatures. The prototype mercury discharge lamp and the experimental conditions are as follows.

Lamp tube diameter: Approximately 18mm
Lamp length: about 1010mm
Gas type: Ar100%
Gas pressure: 600Pa
Lighting circuit: High frequency inverter Lighting frequency: Approximately 60kHz
The experiment was performed under the conditions where the ambient temperature was 25, 10, 0, and −10 (° C.), and when the moving streak disappeared when the lamp tube wall was visually observed from a point approximately 50 cm away from the lamp. The cold spot temperature was measured.

FIG. 13 is a diagram illustrating the relationship between time and the coldest spot temperature.
The black dots plotted on each curve indicate the coldest spot temperature and time when the moving stripes no longer appear. According to FIG. 13, if the ambient temperature is 25 (° C.), no moving fringe is observed immediately after lighting, but if the ambient temperature is 0 (° C.), no moving fringe is observed after about 150 seconds. As the coldest spot temperature increased, no moving stripes were observed. By plotting the points where no moving fringes are observed even at ambient temperatures such as 10 (° C.) and −10 (° C.) by the same method, moving fringes are not observed if the coldest spot temperature is higher than about 25 ° C. I found a common point. When the same experiment was conducted by changing the gas type and gas pressure, the temperature at which the coldest spot temperature was not observed changed, but if the lamp was determined, the temperature would be above the same coldest spot temperature regardless of the ambient temperature. Moving stripes are not observed.

As mentioned above, although the backlight apparatus was demonstrated based on embodiment, this invention is not limited to these embodiment. For example, the following modifications can be considered.
(1) Although only the backlight device has been described in the embodiment, the present invention can also be applied to a general lighting device.
(2) In the embodiment, the description has been made on the assumption of a straight tubular mercury discharge lamp. However, the present invention is not limited to this, and the present invention can also be applied to a U-shaped mercury discharge lamp. In the case of a U shape, the substantially central portion in the tube axis direction corresponds to a portion bent in a U shape.

  As a utilization example of the present invention, a backlight device for a liquid crystal display or the like, a general lighting fixture, or the like can be considered.

1 is a diagram illustrating a schematic configuration of a backlight device according to Embodiment 1. FIG. It is a figure which shows the external appearance of the electrical resistance member 3. FIG. It is a figure which shows the modification of the electrical resistance member. 3 is a circuit diagram showing details of a lighting circuit 2 according to Embodiment 1. FIG. The high frequency voltage waveform which the lighting circuit 2 outputs is shown. It is a figure which shows the relationship between a lamp current and the coldest spot temperature. It is a figure which shows the relationship between a lamp current and a lighting frequency, and the relationship between the electric current for a heating, and a lighting frequency. 6 is a circuit diagram showing details of a lighting circuit 2 according to Embodiment 2. FIG. 6 is a circuit diagram showing details of a lighting circuit 2 according to Embodiment 3. FIG. 6 is a circuit diagram showing details of a lighting circuit 2 according to Embodiment 4. FIG. It is a figure which shows the time change of the voltage applied to the mercury discharge lamp 1 (fluorescent lamp). It is a figure which shows schematic structure of a liquid crystal display. It is a figure which shows the relationship between time and the coldest spot temperature. It is a figure which shows the structure of the lamp lighting device disclosed by patent document 1. FIG. It is a figure which shows the structure of the lamp lighting device disclosed by patent document 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mercury discharge lamp 2 Lighting circuit 3 Electrical resistance member 4 Case 5 Reflector 6 Wiring 7 Liquid crystal panel 8 Wiring 21 Drive circuit 22 Lighting frequency setting circuit 31 Curved part 32 Adjacent part 33 Non-adjacent part

Claims (9)

A mercury discharge lamp in which internal electrodes are arranged at both ends of the glass tube;
An electric resistance member made of an electric resistance material, and arranged so as to be in contact with the outer peripheral surface of the substantially central portion of the mercury discharge lamp glass tube in the tube axis direction;
A high-frequency voltage applying means for applying a high-frequency voltage between the internal electrode and the electric resistance member, and applying a high-frequency voltage between the internal electrodes disposed in the mercury discharge lamp. Light equipment. The electrical resistance member is
A curved portion having a curved surface along the outer peripheral surface of the glass tube of the mercury discharge lamp;
2. A support portion that is fixed to a backlight device housing and supports the curved portion in a state in which a glass tube of the mercury discharge lamp is fitted on a curved surface of the curved portion. The backlight device described in 1. The backlight device according to claim 2, wherein an electrical resistance value of a portion adjacent to the curved portion of the support portion is larger than an electrical resistance value of a portion not adjacent to the curved portion.   The backlight device according to claim 2, wherein an electric resistance value of the curved portion is larger than an electric resistance value of the support portion. The high frequency voltage applying means includes
A high frequency power supply unit that outputs a high frequency voltage of a predetermined frequency;
A first resonance circuit having a first resonance frequency inserted in a wiring for applying a high-frequency voltage output by the high-frequency power supply unit between the internal electrodes;
And a second resonance circuit having a second resonance frequency inserted in a wiring for applying a high-frequency voltage output from the high-frequency power supply unit between the internal electrode and the electric resistance member. The backlight device according to claim 1. The backlight device further includes:
Frequency setting means for setting a frequency of a high-frequency voltage output from the high-frequency power supply unit to a frequency according to a dimming ratio in a frequency region sandwiched between the first resonance frequency and the second resonance frequency. The backlight device according to claim 5, further comprising: The backlight device further includes:
The frequency of the high frequency voltage applied between the internal electrode and the electric resistance member is set to a first frequency until a predetermined period elapses after application of the high frequency voltage between the internal electrodes is started. A frequency setting means is provided for setting a frequency of a high-frequency voltage applied between the internal electrode and the electric resistance member to a second frequency lower than the first frequency when the period has elapsed. The backlight device according to claim 1. The backlight device according to claim 1, wherein the mercury discharge lamp is a hot cathode fluorescent lamp. A mercury discharge lamp in which internal electrodes are arranged at both ends of the glass tube;
An electric resistance member made of an electric resistance material, and arranged so as to be in contact with the outer peripheral surface of the substantially central portion of the mercury discharge lamp glass tube in the tube axis direction;
A high-frequency voltage applying unit that applies a high-frequency voltage between the internal electrode and the electric resistance member while applying a high-frequency voltage between the internal electrodes disposed in the mercury discharge lamp. apparatus.

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